Journal of Superconductivity and Novel Magnetism最新文献

Silver-doped Bi_1/2Na_1/2-xAg_xTiO₃ (BNAT) ceramics (x = 0.0, 0.025, 0.075, and 0.1) were synthesized using the solid-state reaction (SSR) technique. The structural analysis was performed using the X-ray diffraction (XRD) technique, which revealed the formation of a polycrystalline sample with R3c symmetry. Pristine Bi_0.5Na_0.5TiO₃ (BNT) ceramics exhibited an average crystallite size of ~25.372 nm. Doping a small amount of Ag⁺ ions in place of Na⁺ ions resulted in an improved average crystallite size of ~26.365 nm, as calculated by Debye-Scherrer’s formula. Raman spectra were employed to investigate the vibrational modes of the materials. The FTIR spectra of Ag⁺-doped BNT ceramics displayed two strong peaks at ~971 and 537 cm⁻¹, attributed to the presence of metal-oxygen bonds. Room temperature dielectric constant (ε′) and dielectric loss (tan δ) analyses were conducted in the frequency range of 20 Hz to 1 MHz. Complex impedance and modulus spectroscopic analyses indicated the presence of grain boundary effects alongside the bulk contribution and also confirmed the presence of non-Debye relaxations in the materials.

Breast cancer is one of the deadliest cancers for women, so cell labeling and therapy of breast cancer become imperative. In this work, dextran- and carboxymethyl dextran–coated Fe₃O₄ nanoparticles (Fe₃O₄@DEX and Fe₃O₄@CMD) were well synthesized through the co-precipitation method. The dextran and carboxymethyl dextran coating reduces the average particle size of Fe₃O₄ nanoparticles from 10.9 to 4.0–5.5 nm, and the coated samples exhibit average hydrodynamic diameters ranging from 31 to 110 nm. The coating promotes the dispersibility of nanoparticles. Saturation magnetization is reduced from 60.3 to 5.6–7.1 emu/g in the coated MNPs due to the large weight ratio of the coating layer and the decrease in particle size. Hemolysis and cytotoxicity assay results indicate the excellent biocompatibility of Fe₃O₄ nanoparticles. The cellular uptake assay confirms that both dextran- and carboxymethyl dextran–coated Fe₃O₄ nanoparticles are easily taken in by breast cancer cells. Comprehensively considering dispersion, biocompatibility, and cellular uptake, the Fe₃O₄@CMD is more suitable for application in the bio-labeling of breast cancer cells. The SAR values of the Fe₃O₄@DEX and Fe₃O₄@CMD range from 19.2 to 30.7 W/g. The SAR value is mainly influenced by the hydrodynamic diameter in the coated samples. The Fe₃O₄@CMD20 shows the maximum SAR value of 30.7 W/g and has potential application in magnetic hyperthermia therapy.

A comprehensive analysis on conventional rod core fluxgate magnetometer has been done by designing multiple designs with varying number of turns of excitation coil (from hence will be referred to as EXC) and pick-up coil (PC) as well as different core diameter have in Ansys Maxwell and their electromagnetic simulations have been carried out, the results were analysed and are reported in this paper. Also, the current sweep analysis, frequency sweep analysis has been done to study the behaviour of the ferromagnetic core for different magnitudes of excitation current as well as for studying the variation in output induced voltage for different frequencies of the input excitation current. Finally, the electromagnetic simulation of 100 turns rod core design with different ferromagnetic core materials such as iron, ferrite, Metglas 2605 HB1M and Mu-metal has been done to study the sensor performance in terms of sensitivity. The results of all these conducted studies have been included in this paper.

Impact of shot peening on SS347 tube has been investigated using MagStrics, a magnetostrictive sensing (MsS) device comprising of rapidly quenched ribbon as sensor element. Two tubes of SS347 have been considered in pre- and post-shot peened state. Annealed ribbon as sensor element showed enhanced MsS signal. Using the annealed ribbon as sensor element, the MsS signal amplitude in shot peened tube was found to be distinctly different from un-peened sample. This was associated to magnetic phase evolutions in the pipe internal surface due to shot peening. Such phenomena have been endorsed through SEM–EDX compositional analysis and correlated through simulations using COMSOL Multiphysics.

Understanding and controlling the magnetic behavior of nanowire (NW) arrays is a fundamental step for developing novel future-generation devices. The current research investigated the role of copper pre-plating thickness on the structural and magnetic interactions of cobalt NW arrays. The NWs were grown in the anodic aluminum oxide (AAO) templates with a nanopore diameter of 30 nm by using a pulse electrodeposition (PED). The thickness of Cu pre-plating varied by adjusting the amount of electrodeposition (ED) Coulomb charge to about 0.03–0.7 C. The intensity of the Co-hcp peaks in the X-ray diffraction (XRD) pattern changes with the increase of Cu pre-plating, which can be related to ion mobility and growth kinetics during the ED process. The hysteresis curves indicate that effective magnetic anisotropy fields (({text{H}}_{text{A}}^{text{eff}})) increase from 7200 to 11,000 Oe with increasing Cu thickness. The coercivity of Co nanowire arrays without Cu pre-plating was 1170 Oe and rose to 1870 Oe for optimum Cu thickness with 0.3 C pre-plating. The switching field distribution (SFD) extracted from hysteresis curves agrees well with the squareness ratio. Also, the SFD indicates an exchange coupling between the interfaces of the magnetic phases in the optimum sample. The regions formed in the first-order reversal curve (FORC) diagram showed crystalline features and magnetic phase interactions between the intra and inter-wire. Further, the FORC analysis showed the same crystalline features as those obtained from the XRD structural analysis.

Conventional solid-state reaction method has been cautiously employed to prepare the Ba_0.75Sr_0.25Ti_1−xMn_xO₃ ceramic where Sr was firmly doped at the Ba site and Mn was doped with different densities at the Ti site. Since the performance of materials varies with frequency, electric field, and temperature, we have elucidated the various features of the synthesized samples for the sake of scientific benefit in the fields of microelectronics, telecommunications, and spintronics. Structural and morphological features of the ready samples were examined by X-ray diffraction and scanning electron microscopy (SEM). The crystal's tetragonal behavior was verified by XRD analysis, and with the increment of Mn content, the volume of the unit cell is little changed. It is clear from the SEM images that the grain size of the prepared samples increases with Mn doping. The dielectric properties of Ba_0.75Sr_0.25Ti_1−xMn_xO₃ were measured by dielectric constant and AC conductivity in a wide range of frequency from 1 kHz to 10 MHz. This result also explores that the dielectric constant rises with the concentration of Mn, most significantly for the 20% Mn substitution with Ti. We also found from the experimental result that the dielectric constant is high in the frequency range of 1–10 kHz. The magnetic permeability of the prepared sample increased with 10% and 20% of Mn replacement. Ferromagnetic features with a weak coercive field and the increased ferromagnetic order with rising Mn concentrations of the prepared samples were confirmed by VSM data analysis. The developed multiferroic materials can be employed in future spintronic devices like spin transistors, sensors, spin diodes, and memory devices.

In this paper, we report a systematic study on effect of film thickness and substrate temperature on structural and magnetic behaviour of Fe-Ga films with Cu buffer layer, deposited on Si and Si/SiO₂ substrates at room and high substrate temperatures. Grazing incidence X-ray diffraction studies reveal that all the films are crystalline with disordered alpha-Fe phase, which is BCC A2 phase. At 300 °C of substrate temperature, films deposited on Si/SiO₂ substrate found to nucleate L1₂ phase from matrix of A2 phase, which is not seen in Si based films. Irrespective of substrate material, Fe-Ga films found to exist in dual phases at 500 °C substrate temperature. Lattice strains of the films were calculated from X-ray diffraction patterns, using Williamson-Hall method. From X- ray reflectivity analysis of all the films, film density, thickness and roughness of Fe-Ga layer and buffer layer were obtained after fitting the reflectivity data. Presence of an oxide layer is also evident from reflectivity fitting analysis. From magnetization studies it is clear that, all the films exhibited strong in-plane anisotropy. Saturation magnetization of films was found to vary with change in film density and oxide layer thickness of films. Saturation magnetization of films deposited on Si substrates found to decrease with decrease in film density. Coercivity of films found to vary with change in crystallite size, interface roughness and lattice strain of films. Films deposited on Si substrates are sensitive to strain with change in film thickness and films deposited on Si/SiO₂ substrates are sensitive to strain with change in deposition temperature. Coercivity in films found to decrease with decrease in film roughness, increase in crystallite size and lowering the tensile lattice strain.

ZnO-CuO nanocomposite particles (NCPs) were synthesized at different molar ratios (4:1, 3:2, and 1:4) through the use of the co-precipitation technique, which produced interesting modifications in the particle’s physical characteristics. XRD showed that average crystallite size (D_avg) decreased noticeably from about 22.07 to 15.98 nm as the concentration of CuO increased within the ZnO matrix. This pattern points to a major impact of CuO content on the composite’s structural properties. Fourier-transform infrared spectroscopy (FTIR), two distinct functional groups were identified: v₁ and v₂, which were detected at approximately 524 cm⁻¹ and 427 cm⁻¹, respectively, and were linked to intrinsic and extrinsic vibrations. These spectral characteristics highlight the complex interaction between ZnO and CuO and offer important insights into the chemical bonding and molecular interactions within the composite system. The ZnO-CuO nanocomposite was subjected to field emission scanning electron microscopy and energy-dispersive X-ray analysis (SEM-EDX) which showed spherical shapes with increments in agglomeration. UV-Vis absorption spectra revealed a blue shift with increasing absorption in the UV region. The energy band gap of ZnO in its pristine state was found to be 3.31 eV, but in the ZnO₄-CuO₁ composition, it increased to 5.48 eV, suggesting that the addition of CuO caused a significant change in the electronic structure. Significantly, ZnO-CuO NCP antimicrobial evaluation demonstrated exceptional antibacterial efficacy against bacterial strains that were both Gram positive and Gram negative, in addition to fungal pathogens. This strong antimicrobial activity highlights the synthetic nanocomposite’s potential use in fighting a range of microbial infections and highlights their bright future in the environmental and biomedical fields.

The perovskite La₂ZnMnO₆ was successfully synthesised using the conventional solid-state reaction. X-ray diffraction shows that the perovskite La₂ZnMnO₆ crystallizes in a monoclinic structure P2₁/n space group, where Zn and Mn atoms are regularly distributed. The Raman spectrum result reveals three peaks at 696 cm⁻¹, 655 cm⁻¹ and 505 cm⁻¹, corresponding to the A_g stretching mode, B_g anti-stretching, and bending vibrations modes of Ni/Co-O and Mn-O bonds in the structure. The experimental value of the band gap energy was calculated using Tauc’s formula and the result reveals a semiconducting behaviour. We investigated the structural, elastic, magnetic, and electronic properties using the spin-polarized density functional theory. The partial density of state indicates that the material exhibits a antiferromagnetic semiconducting behaviour. The antiferromagnetic ordering is explained by the super-exchange interaction between empty e_g orbitals of Mn⁴⁺( ({t}_{2 g}^{3})({e}_{g}^{0})). The obtained Neel temperature is T_N ∼ 28 K which is comparable with the experiment results. Elastic constants and their derivative parameters show a high mechanical stability of this material with a ductile nature. The investigation of the transport properties encompassed an analysis of the electrical conductivity, the figure of merit, the Seebeck coefficient, and thermal conductivity. The results show that electronic and thermal conductivities increase linearly with temperature. The computed values of the figure of merit are close to unity, suggesting that this material is a promising candidate for thermoelectric application.

It is shown that many anomalies observed in underdoped cuprates, including anomalous spectral weight transfer and a large pseudogap, appear to have a common nature due to both the cluster structure of the underdoped phase and the specific mechanism of superconducting pairing. The combined action of these factors leads to the fact that at a temperature T lying in a certain temperature range T_c < T < T*, the crystal contains small isolated clusters that can exist both in superconducting and normal states, randomly switching between them. In this case, below T_c with a very high probability, the cluster is in a superconducting state, and above T*, it is in a normal state, and the interval T_c < T < T* is the region of existence of the so-called pseudogap phase. The temperatures T_c and T* for YBa₂Cu₃O_6+δ were calculated depending on the doping level δ. The calculation results are in good agreement with the experiment without the use of fitting parameters. At a given T in the same temperature range, the time sequence of randomly arising superfluid density pulses from each cluster can be represented as a random process. The effective width Δω_eff of the spectrum of such a random process will be determined by a correlation time, i.e., the characteristic time between successive on/off superconductivity in two different clusters. This time, according to the estimate, is ~ 10⁻¹⁵ s, which corresponds to Δω_eff ~ 1 eV and explains the effect of spectral weight transfer to the high-frequency region. This approach also makes it possible to explain other anomalies observed in the vicinity of T_c: the reversibility of magnetization curves in a certain temperature range below T_c, the anomalous Nernst effect, and anomalous diamagnetism above T_c.